It is previously known in the art to produce interiorly sterile, cup or beaker shaped containers of plastics by thermoforming a sheet or web of polyethylene or polypropylene. In such instance, the sheet or web is heated to a temperature suitable for thermoforming the web--which lies, for the above-mentioned plastics materials, in the range of between 110.degree. and 160.degree. C., and is then fed into a conventional forming machine with the aid of which the thermoforming process takes place under applied vacuum. The web-like continuous, thermoformed containers are filled with their intended contents such as, for example, sterilized food, and are overlaid by a web-shaped sterilized plastic foil which is permanently sealed against the subjacent thermoformed web in the regions around the opening contours of the containers. Finally, the thus filled, sealed containers are separated from one another by incisions in the sealing regions or zones around the container openings.
As has already been mentioned, the thermoforming operation takes place at a temperature within the range of between 110.degree. and 160.degree. C. which, for the above-disclosed plastics, corresponds to those temperatures at which the web is sufficiently "pliable" to be able to be processed or formed under the applied vacuum, and, at the same time, sufficiently "stiff" to result in vacuum-formed containers of the desired uniform material thickness.
The heating and processing times which are normally employed in thermoforming in the above-described manner are between 3 and 20 seconds. In order for a satisfactory sterilization of the web to be obtained at the above processing temperatures of between 110.degree. and 160.degree. C., a very long stay time is, therefore, required for the web at these temperatures, for example 300 min. at 121.degree. C. or 12 min. at 160.degree. C. In order to avoid such unacceptably long stay times, the sterilization of the web must, therefore, take place by a separate preceding sterilization step, using such means as, for example, a hydrogen peroxide bath through which the web is led prior to the heating and the subsequent thermoforming in the forming machine.